Telephone exchange system



Nov. 17, 1931i.l y. a MevirT ErAl.- 1,831,922

TLPH'N' EXCHANGE SYSTEM Filed Fb. 'A l0. 1930 TS wm M AN vR AQM CW T Mw. A 5.5,. w

o" WW E Patented Nov. 17, 1931 UNITED STATES PATENT-)OFFICE MARCELLUS B. MCDAVITT .AND PAUL C. SCI-IWANTES, JR., YORK,y N. Y., AS-

SIG-NORS TO AMERICAN TELEPHONE T-ELEGRAPH COMPANY, A CORPORATION F NEW YORK TELEPHONE EXCHANGE SYSTEM applicati@ mea February 1o, 19,3 ol serial No.V 427,379.

This invention relates to telephone systems and particularly to line circuits in automatic and semi-automatic telephone systems.

The object of this invention is to facilitate' maintenance service in an exchange employing line-finder switches.

Then it is found necessary for maintenance reasons to block the cut-oit relay of a line circuit in an automatic oirice employing line-finder switches, means should bev provided to prevent hunting line-inder switches from seizing the terminals of the associated line as if it were a calling line. Otherwise it is necessary to insulate the contacts ofthe cutod relayto prevent such seizures.

According to this invention the line relay is provided with the usual operating windings and with a holding winding which. is

, connected in parallel with the winding of a cut-oft' relay.V Upon the origination of a call the line relay, which is energized'by its operating windings, connects its holding winding and the winding of the cut-0H:i relay to the associated sleeve terminals in the banks of the line-iinder switches. Upon seizure of the line by one of the line-finder switches the cutoff relay is operated, both the line relay and the cut-off relay being held operated until the calling subscriber replaces the receiver upon the switchhook. When so arranged the blocking of the cut-011' relay in its operated position does not connect the winding of the cut-ofi relay to the sleeve terminal, and it is therefore not necessary to'insulate contacts.

Figure lof the drawing shows a subscribers line circuit, arranged according to this invention, for use in asystem in which automatic switches are employed in extending connections between calling and called subscribers. Fig. 2 shows the front end of the cut-off relay of the line circuit together with a toothpick or other insulating wedge for holding the armature of the relay in itsoperated position. A relay of this type is shown in detail in the patent to E. B. Craft, 1,156,- 671, October 12, 1915. i

Referring to Figure 1, the subscribers station shown schematically at A is connected by the line conductors 11 and 12 vto the line circuit LC, to terminals 21 and 22 in the bank tis to'a first selector (not shown) in the train l of switches used in completing vthe desired connection. When station A is the called station the connection is Vcompleted by a connector switch (not shown) having access to terminals to which theconductors 11, 12 Aand 13 connect. The line-finder, which is represented schematically bypthe brushes 21, 22, and 28 is similar to that disclosed and described inthe patent to Hg' Hovland No. 1,711,682. n

The line relay 14 has threek windings all wound on the same core. The upper and middle windings are normally connected through backV contacts of theMcut-otl' relay 15 to the line conductors 11 and 12, and these windings will hereafterbe referred to as the line windings of relay 14'. The lower winding, which isV permanently connected' in parallel with the winding of the cut-oiiirelay V15, `is sufficiently inductive toholdV relay 14 after it has beenoperated by the energization of its'line windings. But it -is not necessary that` the holding winding be effective, in the circuit over conductor 13, to operate `relay 14 when the line'is seized by a connector switch.

Whenthe subscriber atstation A removes `14 operates in an obvious circuit through its line windings.' With the relay 14 operated,

ground is connected through the upper outer armature and back contact of the cut-oiirelay 15'. and through a front contact of line relay 14 to thegroup conductor 17. With ground connected to conductor 17 an idle line `-a5 .the receiver to originate a call the line relay iinder, having access to lines in the group cut-off relay 15, in parallel with the holding winding of the line relay, to the sleeve terminal 23 in the bank of line-finder LF and to the corresponding terminal in the banks of each line-finder in the same group. These terminals are companion to the terminals to which conductors 11 and 12 are connected. When the brushes of the line-finder LF, which we will assume to be the line-finder used on thisparticular call, make contact with terminals 21, 22 and 23` a circuit is closed from battery through the holding Winding of line relay 14 in parallel with the winding of cut-oil' relay 15, through conductor 18, terminal 23 and the sleeve brush of the linefinder switch, and through the winding of a control relay (not shown) in the line-finder circuit to ground. The control relay `ot the line-finder operates to stop the line-finder brushes on terminals 21` 22 and 23. The cutoil" relay operates to disconnect the line windings of relay 14 from line conductors 11 and 12: but line relay 14 does not release since its holding winding is energized in parallel with the winding of the cut-ofi' relay 15 in the circuit over conductors 13 and 18. The operation of relay 15 is also effective to disconnect `round from the group conductor 17.

When the calh'nq line is extended through the line-under LF to an associated selector. a busy (Qroundl potential is connected from the selector circuit through the sleeve brush ot the line-finder to sleeve terminal 23. so that other line-finders thereafter searching for the contacts of a calling line will not stop on the terminals ot' the line towhich line-finder LF is connected. This busv notential is also extended through the lower contacts ot relay 14 over conductor 13 tothe corresponding sleeve terminal lin the banks of the connector switches which haveV access to the line of station A. so as to prevent seizure of the line by one of these switches on an incoming call. 1 Y

The desired connection is thereafter established, under the control of dial 19 at station A. and the line conductors 11 and 12 are extended to talking battery through the windings of a supervisory or line relay associated with one of the switches used in cmupleting the connection; llVhen the subscriber at station A replaces the receiver unon the switchhook. the supervisory relay through which talking current is supplied) releases thereby causing the busy potential ground) to be disconnected from sleeve terminal 23 and from the sleeve terminals of the connector switches to whichV conductor 13 connects. The line relay14 and the cut-ott' relav lrelease thus rendering the line circuit L@ eifectiye'for use on the next Vcall originated at station A.

When a. connector circuit seizes'the terminals to which conductors 11, 12 and 13 are connected, on an incoming call, the cut-oit relay 15 is energized in the circuit over con-- ductor 13 so as to disconnect the line windings of relay 14 from conductors 11 and 12. The holding winding of line relay 14 is also energized over conductor 13 and relay 14 may or may not operate. It relay 14 operates no lineffinder is started since ground cannot be connected to the group conductor 17 as long as the cut-oli relay is operated.

Should it become necessary to disable the line of station A for maintenance reasons,

the cut-ott" relay 15 may be blocked in its operated position by inserting the toothpick 53 (Figure 2)V between the armature 50 and the back stop 51 so as to force the armature 50, toward the pole piece 52, into its operated position. The blocking of the cut-olil relay in this manner does not interierewith calls originated on other lines in the same subgroup since line relay 14 is not operated and the winding` of relay 15 is not connected to sleeve terminal 23.

It may be desirable to disable the .line both for originating and for receiving calls in which case ground may be connected to conductor 13 by means of the cord 60 and the ground 61. The cut-cti' relay 15 is thus Y operated electrically, instead of being blocked manually, to disconnect the line windings of relay 14 from conductors 11 and 12, and to prevent ground from being connected to group conductor 17. A connector switch is prevented from seizing the terminals of this line because the ground on conductor 13 is effective as a busy or guarding potential. Line relay 14 may or may not operate because of the ground on conductor 13. It relay 14 does not operate, the calling-line pctential is not connected to conductor 18 to cause hunting line-finders to stop on the terminals of this line. And if relay 14 does operate, the ground on conductor 13 is extended over conductor 18 to constitute a busy or guarding potential to prevent hunting line-finders from stopping on the terminals of this line.

It may be found preferable to have the lower winding of line relay 14 ineffective to operate this relay. When so arranged the busy ground, connected to conductor 13 by a connector switch on an incoming call or connected to conductor 13 for maintenance purpose as described in the preceding paragraph, is not extended to conductor 18. One

advantage of this arrangement is to prevent l any retardation of the hunting movementot a line-finder whenever the terminals ot such a line' are encountered.

It should also be noted that, since the line relay is held operated after the cut-oil relay operates, it is no longer necessary that the line relay be slow in releasing.

What is claimed is:

Y1. In a telephone system, a line-finder switch, a connector switch, a terminal bank for each of said switches, a line connected to terminals in the banks of said switches, a line relay for operating when a call is originated over said line, a cut-olif relay for operating when the terminals of said line are seized at either of said switches to disconnect the operating winding of said line Vrelay from said line, a holding winding for said line relay connected in parallel with the winding of said cut-of relay, a sleeve terminal for said line in the bank of said lineinder switch, said sleeve terminal normally having no connection to battery or ground, and contacts of said line relay for connecting said sleeve terminal to battery through the winding of said cut-oii' relay.

2. In a telephone system, a subscribers station, a linedinder switch, a connector switch, line conductors for connecting said station to line terminals in the banks of said switches, a sleeve terminal associated with each set of said lline terminals and normally having no connection to battery or ground, a line relay for operating when a callvis originated at said station, a cut-oil' relay i'or disconnecting the operating winding ot said line relay from said line conductors, a holding winding for said line relay permanently connetted in parallel with the winding of said cut-off relay to the sleeve terminal in the bank of said connector switch, and contacts on said line relay for connecting` the winding of said cut-ofi relay to the sleeve terminal in the bank of said line-iinder switch,

3. In telephone system, a line-finder switch, a line connected to terminals in the bank of said switch, a marking terminal for said line in said bank, said marking terminal normally having no connection with battery or ground, a line relay, a cut-oit' relay, operating windings for said line relay connected to said line under control ot' said cut-off relay, a holding` winding for said line relay in paraL lel with the winding of said cut-oif relay, contacts oi' said line relayV for connecting the winding of said cut-oit'relay to said marking terminal to mark said line as a calling' line, and means for blocking the armature of said cut-oil' relay in its operated position without marking said line as a calling line. Y

4. In a telephone system, a line, a line relay for operating upon the origination oiLl a. call over said line.l a line-iinder switch for extending said line, line and test terminals in the bank of said switch associated with said line, said test terminal normally having no connection with battery or ground, a cut-oil1 relay for disconnect-ing the operating windings of said line relay from said line, a holding winding of said line relay in parallel with the winding of said cut-oi'il relay tei' holding said line relay operated, contacts of said line relay for connecting the winding of said cut-oit' relay to the test terminal of said line to mark said line as a calling line, and means for holding the cut-0E relay operated without a call having been originated or received over said line and without marking said line as a calling line.

5. In a telephone system, a line-finderv switch, a connector switch, a terminal bank` for each of said switches, a line connected to terminals in the banks of said switches, a line relay for operating when a call is originated over said line, a cut-oit relay for operatingl when the terminals of said line are seized at either of said switches to disconnect the operating winding or" said'line relay from said line, a holding winding for said line relay connected in parallel with the winding ofA said cnt-off relay, a sleeve terminal for said line in ti -e bank of said line-finder switch normally having no connection to battery or ground, contacts ot said line relay for connecting said cut-oli1 relay to said sleeve ter-1` minal. and means for holding the armature oi" said cut-o relay in its operated position.

6. In a telephone system, a subscribers station, a line-finder switch, a connector switch, line conductors for connecting sai'dfv station to line terminals in the banks of said switches, a sleeve terminal associated with each set oi said line terminals, said sleeve terminal normally having no connection with battery or` ground, a line relay for operating.

when a call is originated at said station, a cut-'off relay ier disconnecting` the operating winding of said line relay from said line conductors, aliolding winding for said line relay permanently connected in parallel with thel winding of said cut-off relay to the sleeve terminal in the bank of said connector switch, contacts on said line relay for connecting the winding of said cut-oli relay to the sleeve terminal in the bank of said line-inder switch to mark said line as a calling line, and means for holding the cut-oil relay operated without a call having been originated or received at said subscribers station and without marking' said line as a calling` line.

7. In a telephone system, a line-tinder switch, a connector switch, a. terminal bank for each of said switches, a line connected to termin als in the banks of said switches, a line relayfor operating when a call is originated over said line, a cut-ott relay for operating when the terminals of said line are seized at either of said switches to disconnect the operating winding oi" said line relay from said line, a holding winding for said line relayI vconnected with the Vwinding of said cut-otlI relay, a sleeve terminal ior said line in the bank of said line-finder switch, said sleeve terminal normally having no connection to battery or ground, and contacts of said line relay for connecting said sleeve terminal to battery through the winding of saidcnt-otl7 relay. Y 4 i S. In' a telephone system, a snbscribers station, a line-nder switch, a connector iswitch, line conductors for connecting said station to line terminals in the banks of said switches, a sleeve terminal associated with each set of said line terminals and normally havingno connection to battery or ground, a line relay for operating when a call is originated at-said station, ak cnt-off relay for disconnecting the operating winding of said line relay from said line conductors, a holding winding for said line relay permanently conneced with the winding of said cnt-olf relay tothe sleeve terminal in the bank of said connector switch, and contacts on said 'line relay for connecting the winding of said cut-off relay to the sleeve terminal in the bank ofsaid f line-finder switch.

9. In Va telephone system, a line-linder switch, a line connected to terminals in the bank of said switch, a marking terminal for said line in said bank, said marking terminal normally having no connection with bat- Iterry or ground, a line relay, a cnt-ofi' relay,

operating windings for said line relay connected to said line under control of said cnt-oil' relay, a holding winding for said line relay connected with the winding of said cut-o relay, contacts of said line relay for connecting the winding of said cnt-oil1 relay to said marking terminal to mark said line as a calling line, and means for blocking` the armature of said cnt-oill relay in its operated Y osition without markin0l said line as a callin line.

10. In a telephone system, a line, a line relay for operating upon the origination of a call over said line, a line-linder switch for extending said line, line and test terminals in the bank of said switch associated with said line, said test terminal normally having no connection with battery or ground, a cutofi' relay for disconnectinr the operating windings of said line relay Irom said line, a holding winding of said line relay connected with the winding of said cut-o relay for holding said line relay operated, contacts of said line relay for connecting the winding of said cnt-oliA1 relay to the test terminal of said line to mark said line as a calling line, and means for holding the cnt-off relay operated without a call having been originated or received over said line and without mark ing said line as a calling line.

1l. In a telephone system, a line-finder switch, a connector switch, a termina-l bank for each of said switches, a line connected to terminals in thebanks of said switches, a line relay for operating when a call is originated over said line, a cnt-oli" relay for operating when the terminals of said line are seized at either of said switches to disconnect the operating winding of said linev relay from said line,'a holding winding for said line relay connected with the winding of said cutoii' relay, a sleeve terminal for said line in the bank of said line-finder switch normally having no connect-ion vto battery'or ground, contacts of said line relay for connecting said cut-olil relay to said sleeve terminal, and means for holding the armature of said cntoff relay in its operated position.

12. In a telephone system, a subscribers station, a line-finder switch, a connector switch, line conductors for connecting said station to line terminals in the banks of said switches, a sleeve terminal associated with each set of said line terminals, said sleeve terminal normally having no connection with battery or ground, a line relay for operating when a call is originated at said station, a cnt-olf relay Jfor disconnecting the operating winding of said line relay from said line conductors, a holding winding for said line relay permanently connected with the winding of said cut-oil' relay to the sleeve terminal in the bank of said connector switch, contacts on said line relay for connecting the winding of said cut-oill relay to the sleeve terminal in 'the bank of said line-finder switch to mark said line as a calling line, and means for holding the cut-od relay operated without a call having been originated or received at said subscriber-s station and without marking said line as calling line.

ln testimony whereof, we have signed our names to this specification this 8th day of February, 1930. V

MARCELLUS B. MCDAVITT. PAUL C. SCHlVANTES,Jn.

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